Long-Term Use of Some High Blood Pressure Drugs May Increase Risk of Postmenopausal Breast Cancer

The risk of breast cancer more than doubled among postmenopausal women who took high blood pressure drugs known as calcium-channel blockers for 10 years or longer, according to the results of a study published in JAMA Internal Medicine.

Breast cancer is the second leading cause of cancer death in women in the United States. The chance of an individual developing cancer depends on both genetic and non-genetic factors. Non-genetic factors may include diet, exercise, or exposure to other substances, including medications.

Hypertension—or high blood pressure—is a chronic condition that is often treated with medications known as antihypertensive agents. In fact, antihypertensive agents are the most commonly prescribed class of medications in the United States. There are several different types of antihypertensive agents, including calcium-channel blockers, angiotensin-converting-enzyme (ACE) inhibitors, angiotensin-receptor blockers (ARBs), beta blockers and diuretics.

Although blood pressure medications are widely prescribed, data regarding their long-term impact is sparse. In order to evaluate the relationship between high blood pressure drugs and the risk of invasive ductal and invasive lobular breast cancers among postmenopausal women, researchers conducted a population-based, case-control study in the 3-county Seattle-Puget Sound metropolitan area. The study included 880 women with invasive ductal breast cancer; 1,027 with invasive lobular breast cancer; and 856 women with no cancer who served as the control group. All of the women in the study were aged 55 to 74.

The researchers gathered detailed data regarding health history, obesity, and alcohol and tobacco use as well as the history of hypertension and use of antihypertensive agents—including type, duration, and how recently the drugs were used.

Overall, the use of antihypertensive agents was not associated with an increased risk of breast cancer—regardless of whether the use was classified as current, former, or short-term. However, when the researchers analyzed the results based on the type and duration of antihypertensive therapy, they found that calcium-channel blockers had a significant association with breast cancer risk. In fact, women currently taking calcium-channel blockers who had used them for 10 or more years had two and a half times the risk of developing invasive ductal and invasive lobular cancers compared to women who never used such calcium-channel blockers and compared to users of other forms of antihypertensive agents.

In contrast, the results indicated that other types of antihypertensive agents, such as beta blockers, diuretics, and ARBs, were not associated with an increased risk of breast cancer—even when used long term.

The researchers concluded that long-term use of calcium-channel blockers may be associated with an increased risk of breast cancer among postmenopausal women. More research is needed to confirm this hypothesis and to evaluate the underlying mechanisms.